In the manufacture of quilted fabrics in which, for example, a cover, a liner and one or more layers of filling material are joined to form an article such as a quilted furniture cover or a mattress cover, automated quilting machinery is commonly employed to stitch the layers of material together, with stitching applied in repeated patterns, or arrays of repeated patterns. High speed and economic production of such quilted fabrics generally requires equipment utilizing arrays of needles, ganged together and driven through a common stitch forming mechanism, to apply a plurality of patterns simultaneously in a predetermined array.
In between each stitch of the needle, the layers of fabric are moved in unison with respect to the needles in order to place the next stitch at the desired point in the quilting pattern. Further, with each stitch cycle of the needles, a presser plate is moved toward a needle plate to compact the layers of material for the stitching process. As the needles move out of the material, the pressure plate is simultaneously lifted or moved away from the needle plate, thereby permitting the material to be moved for the next stitch. Normally, the needles are mechanically coupled to and driven by a needle bar rocker shaft that, in turn, is mechanically connected to and driven by a continuously rotating drive shaft. The presser plate is also mechanically connected to and driven by the needle bar rocker shaft. The motion of the presser plate is thus mechanically and constantly fixed with respect to the motion of the needle.
With every stitch cycle, the presser plate starts at the same uppermost position with respect to the needle plate, moves downward to the same lowermost position with respect to the needle plate and then retracts upward to the starting uppermost position. Thus, with each stitch, the pressure plate moves the same distance downward to the same material compaction position and then retracts the same distance to its uppermost starting position. Since the operation of the pressure plate is mechanically fixed throughout the quilting process, the gap between the pressure plate and the needle plate at any point in the stitching cycle is always the same. Therefore, a quilting machine is practically limited to stitching layers of material that have the same thickness. The relative motion of the pressure plate is controlled by cams on a rocker shaft. Therefore, it is possible to change those cams in order to provide a different gap between the pressure plate and the needle plate during the stitching cycle. Even though reconfiguring the quilting machine is possible by changing various cams, the task requires many hours of complex and difficult labor and, therefore is rarely if ever done.
Therefore, as a practical matter, if one desires to stitch a thicker quilt, a different quilting machine is generally used which is configured to have a generally larger gap between the presser plate and the needle plate throughout the stitching cycle. With a thicker quilt, the presser plate must have a higher starting position that allows the thicker quilt to be inserted thereunder and a higher, full compaction position that properly compresses the thicker quilt during the stitching process. The requirement that different quilting machines must be used to stitch quilts having different thicknesses presents significant disadvantages. For example, for those who can afford only one quilting machine, their market is limited to those applications for quilts of the thickness that can be produced on that one machine. In other situations, the commercial demand or quantity of a quilt of a particular thickness may be relatively small; and therefore, the purchase of an automated quilting machine cannot be economically justified. Thus, those markets must be served by quilts that have a higher labor content and thus, are more expensive.
Consequently there in a need for an improved quilting machine that is more flexible in its operation and reconfiguration so that with an easy adjustment quilts of different thicknesses may be stitched.